Process of preventing yellow stain in photographic preparations and regulation of the halogen content thereof



tion.

pounds, during developing brings about a pre- Patented Jan. 11, 1938PATENT OFFICE rnocnss or PREVENTING YELLOW s'ranw IN rno'roonarmcPREPARATIONS AND REGULATION OF TENT THEREOF THE HALOGEN CON- AlbertSteigmann, Lnxemburg-Ville, Luxemburz,

asaignor to Felix Sager & Dr. Gossler Gesellscliatt mit beschriinkter,Haftnng, Heidelberg, Germany, a firm of Germany No nmwing. ApplicationNovember '1, 1936, Se-

rial No. 109,792. In Germany December 13,

14 Claims.

Thisinvention relates to a product and process of preventing yellowstain in photographic prepof thallium salts has a tendency to iorm fogin,

photographic emulsions which is undesirable.

I have discovered that iodonium compounds have all the good propertiesof the thallium salts when used in photographic solutions and they alsoact to prevent fog and particularly yellow stain, while at the sametime, they do not interiere in the least with sensitivity and grada-Furthermore, the use of iodonium comcipitation of silver in the deepestblacks that are non-bronzing and which are free from reflection.

I have found that the use of suitable iodonium salts such as diphenyliodonium nitrate or acetate in photographic preparations makes itpossible to keep the content of halogen ions at a constant valuecorresponding to the solubility of the iodonium halides in theparticular solution. In this manner, an excess of halogen ions in theproduction of photographic emulsions is prevented from the start, whichis of considerable importance in'the preparation of, for example, silveriodide emulsions. The influence upon the formation oithe grain is alsoimportant. Ii iodonium salts in slight quantities are added aftermixing, ripening and subsequent ripening'can be carried out at aconstant low content oi halogen ions. Also, when iodonium .compounds'areadded after ripening, or to the wash water, washing out can be eflectedat a constant .low content of halogen ions, whereby considerableinequalities in washing out the halogen ions in the'outer layers can beavoided.

The addition of these iodonium compounds to a developer also preventsthe troublesome con 1 centra't ion of potassium bromide or iodide.Similarly such addition to the'fixing bath prevents concentration ofiodine ions .which delays fixing. Furthermore the addition of iodoniumcompounds to fixing baths which .have been desilverized and used servesto regenerate the baths so that they may be used again. addition to theaforementioned desirable properties being secured in emulsions anddevelopers by the use of iodonium compounds therein,

these compounds have a marked anti-fog effect when added thereto. Thisanti-fog efiect is present even when the iodonium. compounds are addedto other than the emulsion, as for example to the protective layer, thebacking or even to the paper support for the emulsion.

Furthermore I have found that all of the aforementioned advantages canbe secured by the addition of other compounds which, due todecomposition and/or mutual reaction of the decomposition productsproduce iodonium compounds. As an example of such other compound, I findthat iodosobenzene, in the cold, disintegrates into iodoxybenzene andiodobenzene and these two products react to form the diphenyl iodoniumcompound in the developer.

' The following are two examples of practicing I my invention:

Example 1 least tendency to form yellow stain even during prolongeddevelopment.

Example 2 formation of bromine and iodine ions which in- 1 teriere withdevelopment is prevented, as these ions precipitate as difli'cultlysoluble diphenyl iodonium bromide or iodide. If necessary, the amount ofiodonium compound can be increased according to the quantity ofpotassium bromide and iodide formed.

I claim: 1. The method of preventing yellow stain and regulating thehalogen-ions in light sensitive silver halide emulsions, which consistsin treata ing said emulsions with a solution containing a solubleiodonium compound.

2. The method'of preventing yellow stainand regulating the halogen ionsin light sensitive silver halide emulsions which consists in adding asoluble iodonium compound thereto.

3. The method of preventing yellow stain and regulating the halogen ionsin light sensitive silver halide emulsions which consists in, addingthereto diphenyl-iodonium nitrate.

4. The method oi'preventing yellow stain and.

regulating the halogen ions in light sensitive silver halide emulsionswhich consists in. addi thereto diphenyl-iodonium acetate.

5. The' method of preventing yellow stain and regulating the halogenions in developers which consists in developing an exposed lightsensitive silver halide layer is a solution containing a developingagent and a soluble iodonium compound.

6. The method of preventing yellow stain and regulating'the halogen ionsin developers which consists in adding iodosobenzene to a solutioncontaining a developing agent capable of developing silver halide, saidiodosobenzene disintegrating in the cold into iodoxybenzene andiodobenzene, these two products reacting to form a diphenyl-iodoniumcompound, and developing an exposed light sensitive silver halide layerin said solution.

'7. The method of preventing yellow stain and regulating the halogenions in developers which consists in developing an exposed light sensi-Y tive'silver halide layer in a solution containing a developing agentand diphenyl-iodonium nitrate.

8. The method of preventing yellow stain and regulating the halogen ionsin developers which consists in developing an exposed light sensitivesilver halide layer in a solution containing a developing agent anddiphenyl-iodonium acetate.

9. The method of preventing yellow stain and regulating the halogen ionsin fixing baths which consists in treating an exposed and developedphotographic element in a solution containing a silver halide solventand a soluble iodonium compound.

10. The method of preventing yellow stain and regulating the halogenions in flxing baths which consists in treating an exposed and developedphotographic element in a solution containing a silver halide solventand diphenyl-iodonium acetate.

12. A photographic light sensitive element comprising silver halideemulsiomand a soluble .iodonium compound therein for preventing yellowstain. 4

13. A photographic developer comprising a developing agent capable ofdeveloping a silver halide image, and a soluble iodonium compoundtherein for preventing yellow stain and regulating the halogen ions.

14. A photographic fixing bath comprising a silver halide solvent, and asoluble iodonium compound therein for preventing yellow stain andregulating the halogen ions.

ALBERT STEIGMANN.

